Disbelief after 1.6km-long pile-up

SPRAWLING PILE-UP: Trucks and passenger vehicles block eastbound Interstate 94 following a massive crash that killed three people and injured about 20 near Michigan City, Indiana.

Cars were mangled and some were burned despite the blowing snow. Other vehicles were crushed between jack-knifed semi-tractors, so entwined that it was difficult to tell them apart.

People were screaming, but emergency responders couldn't see many of them as they quickly tended the victims amid frigid conditions.

Within seconds, traffic along snow-covered Interstate 94 in northern Indiana, USA, had become a 1.6km-long pile of debris after whiteout conditions swept in during Thursday's evening commute (local time). Three people were killed and nearly two dozen were injured.

"It was such a devastating scene, you don't know where to start," said Coolspring Township Fire Chief Mick Pawlik, whose volunteer crew was among the first on the scene about 60 miles south of Chicago.

"There were people in cars that you couldn't even see," Pawlik said during a news conference on Friday. "But when people are stuck in their cars, they look at you like we're Moses. 'Part the water. Save us.'"

Rescue crews quickly set about prioritising the victims. Who needed help first? And who was beyond help?

Firefighters worked quickly to keep the victims warm while they extricated them. Just as importantly, Pawlik tried to take their minds off what had happened - even though the dead weighed on his and other first responders' minds.

"Those are the worst," Pawlik said. "You sit there - they're the last ones to get out but you know they're there."

The chain-reaction collision near Michigan City was triggered by a sudden burst of heavy lake-effect snow that took drivers by surprise, said Indiana State Police Lieutenant Jerry Williams. Within about 45 seconds, dozens of vehicles - including numerous other trucks - were crashing into one another.

The accident killed Chicago resident Jerry Dalrymple, 65, and a Michigan couple: Thomas Wolma, 67, and his 65-year-old wife, Marilyn, of Grand Rapids. More than 20 people were injured, including one who remained in critical condition on Friday.

Pawlik said the scene was: "Something that you'll never forget. It'll live with us forever." But he acknowledged that first responders were expecting worse.

"We're lucky that there wasn't 20 people dead and three people injured," he said.

Among the survivors was Jeffrey Rennell, who was driving home to Michigan from a business meeting in Chicago when his SUV suddenly started bouncing off other vehicles like a ping pong ball. Firefighters found it on top of another vehicle and "encased in semis", Pawlik said.

Rennell was trapped for more than three hours in the twisted remains of his Ford Explorer, according to his brother, Steve Rennell. He said his 48-year-old brother told him he wasn't able to move much while trapped in his SUV, but he didn't think his injury was serious.

"There were other people around that he knew weren't all right," Steve Rennell said.

Pawlik said Rennell's extrication was the worst of the five or six that crews did Thursday night.

He kept talking to Rennell throughout the process, even making the Michigan man laugh when he told him: "Jeff, it's after 5 o'clock, and when we get you out I'm going to take you out for a beer."

Instead, Rennell was airlifted to a Chicago hospital, where he was treated for a broken leg and released. He was headed back to Michigan on Friday to be reunited with his wife and two children, ages 5 and 3.

"It was a miracle out there," Pawlik said. "I never want to see it again."

Indiana State Police Sgt. Ann Wojas said the investigation into the crash could take months.

But officials defended the actions of highway crews and praised the efforts of first responders, who spent hours tending to the injured along a frigid mile-long stretch of road.

Indiana Department of Transportation spokesman Matt Deitchley said crews had been out salting and ploughing the area about 20 minutes before the crash. The roads were slick, but conditions didn't warrant closing the road, he said.